Kuske C R, Kirkpatrick B C
Department of Plant Pathology, University of California, Davis 95616.
Int J Syst Bacteriol. 1992 Apr;42(2):226-33. doi: 10.1099/00207713-42-2-226.
Restriction fragments containing the 16S rRNA gene of the western aster yellow mycoplasmalike organism (SAY-MLO) were identified in Southern blots probed with cloned fragments of the western X-disease mycoplasmalike organism 16S rRNA gene. Two fragments which contained the entire SAY-MLO 16S rRNA gene and flanking DNA were cloned in M13 and sequenced. The SAY-MLO 16S rRNA gene is approximately 1,535 bp long, has a G+C content of 47 mol%, and has an overall secondary structure similar to that proposed for Escherichia coli. Putative rRNA promoter sequences and sequences involved in processing of the primary rRNA transcript were similar in the SAY-MLO, two Mycoplasma species, and Bacillus subtilis, suggesting that these prokaryotes and the mycoplasmalike organisms may have similar transcriptional and processing enzymes. We identified two tRNA genes, a tRNA(Tyr) (GTA) gene upstream from the 16S rRNA gene and a tRNA(Ile) (GAT) gene in the spacer region between the 16S and 23S rRNA genes. Comparisons of the SAY-MLO 16S rRNA nucleotide sequence with 16S rRNA sequences of other organisms indicated that the SAY-MLO is phylogenetically related most closely to other plant-pathogenic mycoplasmalike organisms, followed by Anaeroplasma species, Acholeplasma species, and some Mycoplasma species.
在用西部X病类支原体16S rRNA基因的克隆片段探测的Southern杂交印迹中，鉴定出了含有西部紫菀黄化类支原体（SAY-MLO）16S rRNA基因的限制性片段。将包含整个SAY-MLO 16S rRNA基因及侧翼DNA的两个片段克隆到M13中并进行测序。SAY-MLO 16S rRNA基因长度约为1535 bp，G+C含量为47 mol%，其整体二级结构与大肠杆菌的二级结构相似。推测的rRNA启动子序列以及参与初级rRNA转录本加工的序列在SAY-MLO、两种支原体和枯草芽孢杆菌中相似，这表明这些原核生物和类支原体可能具有相似的转录和加工酶。我们鉴定出两个tRNA基因，一个位于16S rRNA基因上游的tRNA(Tyr)（GTA）基因，以及一个位于16S和23S rRNA基因间隔区的tRNA(Ile)（GAT）基因。将SAY-MLO 16S rRNA核苷酸序列与其他生物的16S rRNA序列进行比较表明，SAY-MLO在系统发育上与其他植物致病类支原体关系最为密切，其次是厌氧支原体属、无胆甾原体属和一些支原体属。
